Lady slippers (Cypripedium montanum), the largest orchids in California, grow to a height of 18 to 24 inches. Each plant usually bears one or two flowers 2 ½ inches across. The white lip of each flower protrudes about an inch and a half. Lady slipper orchids are so striking that we here in Yosemite do not advertise their specific location over concern that unscrupulous individuals may dig these rare beauties up and try to grow them at home. They have such specific needs that they are virtually impossible to grow outside their native habitat.
http://www.nps.gov/yose/blogs/Lady-Slipper-Orchids.htm